Gas generator for an air bag

ABSTRACT

A gas generator for an airbag producing no malfunction is provided.  
     When the first combustion gas generated in the first combustion chamber  30  enters the filter chamber  50 , most of the gas is discharged through the gas discharge port  52 , however, part of the combustion gas flows into the second through hole  62 . This combustion gas flows through the vent hole  76  into the second combustion chamber  40  after changes its flow direction by the gas-flow inhibiting member  80  inside the second cap member  75 . At this time, the temperature of the gas is lowered, so that the second gas generating agent  43  is never burnt.

TECHNICAL FIELD

The present invention relates to a gas generator for an airbag used inan airbag system for an automobile.

BACKGROUND ART

So-called dual-type gas generators are used for the purpose ofregulating the developing speed or the degree of tension of an airbag inresponse to, for example, the magnitude of the impact at a vehiclecollision and the physique of the passenger.

In dual-type gas generators, two combustion chambers (gas generatingportion) are independently operated to adjust an amount of a gasgenerated and a discharging speed of a gas to the airbag. Accordingly, asituation in which, as a result of the ignition of the gas generatingagent of one combustion chamber, the gas generating agent of the othercombustion chamber is ignited is a malfunction.

Although such a malfunction can be prevented by completely separatingthe two combustion chambers and the gas discharge passages, this resultsnot only in an increase in the number of component parts but also anincrease in the weight and the scale of the gas generator itself, whichcontrasts with the demand for the compacting and weight-reductionthereof.

In U.S. Pat. No. 5,970,880, the combustion chambers are arranged in bothends of a housing, a safety valve 26 is provided in the right sidecombustion chamber to prevent the effect of the left side combustionchamber from transferring to the right side through a communication hole6.

However, in order to ensure that the gas of the right side combustionchamber is discharged through the communication hole 6 to a centralfilter chamber and to prevent the gas from passing through the left sidecombustion chamber, the plate thickness of a section 28 and the width orplate thickness of a section 39 of the safety valve 26 should beadjusted and, depending on differences in an amount of a gas generatingagent charged therein and a size of the communication hole 6, thisshould be re-adjusted.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a gas generator for anairbag in which, in a dual-type gas generator, such a malfunction thatbecause of the combustion of a gas generating agent in one combustionchamber, a gas generating agent of another combustion chamber is burntis prevented, and in which the structure can be simplified.

As a means of solving the problem, the present invention provides a gasgenerator for an airbag, comprising two combinations of an ignitionmeans and a combustion chamber including a gas generating agent, the twoignition means capable of being activated separately from each otherwith a time lag,

-   -   the gas generator having a structure such that part of the        combustion gas possibly flows from the gas discharge passage        into the other combustion chamber in a procedure where one of        the ignition means is activated first, the gas generating agent        in one of the combustion chambers is ignited and burnt first to        generate a combustion gas and the combustion gas flows in a gas        discharge passage and is discharged from a gas discharge port to        inflate an air bag,    -   at least one flame-transferring preventing means being provided        at a given position in the passage where the combustion gas        flows from the gas discharge passage into the other combustion        chamber for obstructing direct advance of the combustion gas        flow.

By arranging the flame-transferring preventing means as described aboveto obstruct direct advance of the combustion gas flow (first combustiongas flow) generated in the one combustion chamber (first combustionchamber) that is ignited and burned first, such a malfunction isprevented that a gas generating agent in the other combustion chamber(second combustion chamber) to be ignited and burnt with delay isignited and burned by the first combustion gas flow.

Accordingly, by obstructing direct advance of the first combustion gasflow, preferably by diverting the gas flow, the first combustion gasflow strikes repeatedly against component parts, and thereby, thefollowing actions are exhibited:

-   -   (i) the flame blocking action in which a flame is blocked so        that it cannot reach the second combustion chamber,    -   (ii) the temperature lowering action in which the temperature of        the first combustion gas is lowered, and    -   (iii) the mist reduction action in which mists (solid components        in the gas generating agent generated by the combustion of the        gas generating agent. For example, metal components) contained        in the first combustion gas flow is reduced by colliding against        a constituent part and adhering thereto.

The ignition and combustion of the gas generating agent in the secondcombustion chamber is prevented by the flame-transferring preventionaction comprising the flame blocking action, gas temperature loweringaction and mist reduction action obtained by the flame-transferringpreventing means. As a result, a malfunction is prevented and the gasgenerating agent in the second combustion chamber is normally ignitedand burned by the activation of the ignition means. It should be notedthat the mist reduction action obtained by the flame-transferringpreventing means provides the additional effect of reducing an amount ofmists to flow into the airbag.

The flame-transferring prevention action obtained by thisflame-transferring preventing means prevents the ignition and combustionof a gas generating agent in the one combustion chamber caused by theactivation of another ignition means not only in the ignition mode suchthat the two ignition means are activated with a time lag but also inthe ignition mode such that only one ignition means is activated and theother ignition means is not activated (when only a small amount ofgenerated gas is sufficient).

Two or more flame-transferring preventing means can be arranged atdifferent positions and, for example, when a plurality thereof are to bearranged, these may be arranged in a communication passage(communication space) located between the first combustion chamber andthe second combustion chamber, or they may be arranged in the secondcombustion chamber.

It should be noted that in order to increase or decrease a generatedamount of a gas by means of increasing or decreasing a charged amount ofa gas generating agent, the width (cross-sectional area) of the gasdischarge passage is increased or decreased by changing positions of theflame-transferring preventing means.

In the gas generator for an air bag according to the present invention,preferably, the flame-transferring preventing means comprises acombination of a cap member and a gas-flow inhibiting member arranged inthe interior of the cap member,

-   -   the cap member comprises a ceiling surface and a side surface        having a plurality of vent holes, the opposite side of the        ceiling surface comprises an opening portion, and    -   the gas-flow inhibiting member is arranged such that, when a        combustion gas (a first combustion gas) flows from the gas        discharge passage and enters the cap member through the opening        portion of the cap member, the direction of the combustion gas        (first combustion gas) is changed by the gas-flow inhibiting        member and then the gas flow enters, through the vent holes of        the side surface, the other combustion chamber (second        combustion chamber) in which combustion is started with delay.

The flame-transferring preventing means comprises a combination of thecap member and the gas-flow inhibiting member arranged in the interiorof the cap member and thereby, a passage through which the firstcombustion gas flow enters the second combustion chamber and a passagethrough which a second combustion gas flow reaches a gas discharge portare made zigzag, so that the flame-transferring prevention action isenhanced.

In the gas generator for an air bag according to the present invention,preferably, the flame-transferring preventing means comprises a sealtape, and by the seal tape, the combustion gas flow (first combustiongas flow) is prevented from entering the other combustion chamber(second combustion chamber) in which combustion is started with delay.The flame-transferring prevention action is enhanced by the combinationof the seal tape and the cap member.

In the gas generator for an air bag according to the present invention,preferably, the flame-transferring preventing means comprise a wire meshor coolant/filter, so that the combustion gas flow (first combustion gasflow) flows, through the wire mesh or coolant/filter, into the othercombustion chamber (second combustion chamber) in which combustion isstarted with delay.

The flame-transferring prevention action is enhanced by the arrangementof the wire mesh or coolant/filter.

In the gas generator for an air bag according to the present invention,preferably, the gas discharge passage comprise a structure forobstructing the direct advance of the combustion gas flow (firstcombustion gas flow).

For example, in such a structure that an opening portion is provided atboth ends of the space forming the gas discharge passage and that thetwo opening portions never faces each other directly in the axialdirection (the flow direction of the first combustion gas flow), thefirst combustion gas flow does not advance directly from the openingportion at one end to the opening portion at the other end but flowsinto the opening portion at the other end after striking against aninner wall surface, and thereby, the flame-transferring preventionaction is enhanced.

In the gas generator for an airbag of the present invention, acoolant/filter is arranged, separately to the flame-transferringpreventing means, in the gas discharge passage that leads to the gasdischarge port, and when part of the combustion gas flows into the othercombustion chamber, the combustion gas always passes through thecoolant/filter to enter the other combustion chamber because of theaction of the flame-transferring means for obstructing a direct advanceof the combustion gas flow.

The combustion gas generated in the one combustion chamber passesthrough the coolant/filter (the filter for arresting combustion residuesand cooling the gas), which enhances the flame-prevention action.Consequently, even when the combustion gas enters the other combustionchamber, a gas generating agent stored therein is never ignited andburnt.

As another means for solving the problem, the present invention providesa gas generator for an airbag, comprising a first ignition means and afirst combustion chamber accommodating a first gas generating agent inone end side of a cylindrical housing, and a second ignition means and asecond combustion chamber accommodating a second gas generating agent inthe other end side of a cylindrical housing,

-   -   a first partition wall having a first through hole and a second        partition wall having a second through hole defining a separated        space between the first combustion chamber and the second        combustion chamber, a space formed between the first partition        wall and the second partition including a filter chamber        provided with a cylindrical filter,    -   the cylindrical housing having a gas discharge port provided in        the surface directly facing the cylindrical filter,    -   a cap member being provided as a flame-transferring preventing        means in the second combustion chamber,    -   the cap member having a ceiling surface and a side surface        having a plurality of vent holes, provided with an opening        portion in the opposite side of the ceiling surface, the cap        member covering the second through hole from the opening portion        side, being fixed onto the second partition wall.

Because the first combustion chamber and second combustion chamber arein communication with each other through the filter chamber, part of thefirst combustion gas flow generated in the first combustion chamber maypass through the filter chamber and flow from the second through holeinto the second combustion chamber. In view of the above, by arrangingthe cap member, which corresponds to the flame-transferring preventingmeans, in the second through hole, the above flame-transferringprevention action is exhibited.

The flame-transferring prevention action obtained by theflame-transferring preventing means prevents the ignition and burning ofthe second gas generating agent in the second combustion chamber causedby the activation of the first ignition means, not only in such anignition mode that a first and a second ignition means are activatedwith a time lag but also in such an ignition mode that only a firstignition means is activated and a second igniter is not activated (whena small amount of generated gas is sufficient).

It should be noted that, in order to enhance the moisture-proof of thefirst combustion chamber and second combustion chamber or to maintainthe initial stage pressure of combustion in the respective combustionchambers, the first through hole and second through hole may be closedby a seal tape mede of aluminum or stainless steel.

In the gas generator for an air bag according to the present invention,preferably, the flame-transferring preventing means comprises acombination of a cap member and a cylindrical gas-flow inhibiting memberarranged in the interior of the cap member,

-   -   a cylindrical gas-flow inhibiting member is concentrically        provided inside the cap member to have one end opening portion        facing the second through hole and the other end opening portion        facing the ceiling surface of the cap member, and    -   when the combustion gas flows through the second through hole        into the cap member, the direction thereof is changed by the        gas-flow inhibiting member, and then the gas flow enters the        second combustion chamber through the vent holes in the side        surface.

The flame-transferring preventing means comprises the cap member and thegas-flow inhibiting member disposed inside the cap member and thereby, apassage through which the first combustion gas flow enters the secondcombustion chamber and a passage through which the second combustion gasflow reaches a gas discharge port are made zigzag, so that theflame-transferring prevention action is enhanced.

In the gas generator for an air bag according to the present invention,preferably, the flame-transferring preventing means comprises a sealtape, and the vent holes of the cap member are closed by the seal tape.The flame-transferring prevention action is enhanced by the combinationof the seal tape and the cap member.

In the gas generator for an air bag according to the present invention,preferably, the flame-transferring preventing means comprises a wiremesh arranged between the side surface of the cap member and the sidesurface of the gas-flow inhibiting member, whereby the combustion gas iscaused to flow into the other combustion chamber in which the initiationof combustion is delayed after passing through the above wire mesh.

Preferably, the wire mesh is formed cylindrical by laminating aplurality of wire meshes having a loose structure (such as a mesh wovenfilter formed by compression-molding a plain woven wire mesh, anexpanded metal, punched metal or metal lath wire mesh, or a metal wirerod). The flame-transferring prevention action is enhanced by thearrangement of such a wire mesh.

In the gas generator for an air bag according to the present invention,preferably, the flame-transferring preventing means comprises acoolant/filter disposed between the ceiling surface of the cap memberand the other end opening portion of the gas-flow inhibiting member, thecombustion gas is caused to flow through the coolant/filter into theother combustion chamber in which the initiation of combustion isdelayed.

It is preferable that the coolant/filter is formed into a disk-likeshape by laminating a plurality of loose wire meshes (such as the aboveloose wire mesh).

The flame-transferring prevention action is enhanced because thetemperature of the first combustion gas flow is likely to be furtherlowered by the arrangement of such a coolant/filter.

In the gas generator for an air bag according to the present invention,preferably, a covering member, which prevent the direct advancement ofthe combustion gas flow to the second through hole, is provided on thesecond partition wall surface inside the filter chamber. Theflame-transferring prevention action is enhanced by the arrangement of acovering member together with the cap member.

It is preferable that, in the gas generator for an airbag of the presentinvention, no part of the first through hole directly faces any part ofthe second through hole in the axial direction.

Most of the first combustion gas flow, entering the filter chamber fromthe first through hole, flows to the gas discharge port, however, evenwhen part of the combustion gas flows toward the second through hole, itdoes not advance directly from the first through hole toward the secondthrough hole but flows from the second partition hole to the secondcombustion chamber after striking against the second partition surface,so that the flame-transferring prevention action is enhanced.

As another means for solving the problem, the present invention providesa gas generator for an airbag, comprising a first ignition means and afirst combustion chamber accommodating a first gas generating agent inone end side of a cylindrical housing, and a second ignition means and asecond combustion chamber accommodating a second gas generating agent inthe other end side of a cylindrical housing,

-   -   a first partition wall having a first through hole and a second        partition wall having a second through hole defining a separated        space between the first combustion chamber and the second        combustion chamber, a space formed between the first partition        wall and the second partition wall including a filter chamber        provided with a cylindrical filter,    -   the cylindrical housing having a gas discharge port provided in        the surface directly facing the cylindrical filter, wherein    -   at least one gas flow diversion members being disposed in the        filter chamber to forcibly make the combustion gas flow enter        the cylindrical filter when the combustion gas generated in the        first combustion chamber flows into the filter chamber from the        first through hole.

The combustion gas generated in the first combustion chamber is causedto flow through a filter (coolant/filter), and thereby, theflame-transferring prevention action is enhanced, so that even when theabove combustion gas flows in the second combustion chamber, the secondgas generating agent therein is never ignited and burnt.

In the gas generator for an air bag, the gas flow diversion membercomprises a ceiling surface and a circumferential surface having aplurality of vent holes, and an opening portion is provided in theopposite side of the ceiling surface,

-   -   a single gas flow diversion member can be arranged such that a        gap corresponding to a passage for gas flow is secured between        the second through hole and ceiling surface, the circumferential        surface abuts against the inner circumferential surface of the        cylindrical filter and the diversion member covers the first        through hole at the opening portion side and is fixed to the        first partition wall.

By the arrangement of such a single gas flow diversion member, when thecombustion gas generated in the first combustion chamber flows from thefirst through hole into the filter chamber, the combustion gas isforcibly caused to flow through the holes in the circumferential surfaceof the gas flow diversion member towards the cylindrical filter. Andmost of the gas is discharged, after filtered and cooled, through thegas discharge port, however, part of the gas is not discharged throughthe gas discharge port and it flows into the second combustion chamberthrough the second through hole. Even in such a case, because of theflame-transferring prevention action obtained by the filter, the secondgas generating agent is never ignited and burn. It should be noted that,when a single gas flow diversion member is used, it may also be arrangedat the second through hole.

In the gas generator for an airbag of the present invention, two gasflow diversion members is provided,

-   -   among these, a first gas flow diversion member, which comprises        a ceiling surface, a circumferential surface having a plurality        of vent holes and a opening portion provided in the opposite        side of the ceiling portion, is arranged such that the        circumferential surface abuts against the inner circumferential        surface of the cylindrical filter and the diversion member        covers the first through hole at the opening portion side and is        fixed to the first partition wall,    -   a second gas flow diversion member, which comprises a ceiling        surface, a circumferential surface having a plurality of vent        holes and a opening portion provided in the opposite side of the        ceiling portion, is arranged such that the circumferential        surface abuts against the inner circumferential surface of the        cylindrical filter and the diversion member covers the second        through hole at the opening portion side and is fixed to the        second partition wall, and    -   the ceiling surface of the first gas flow diversion member and        the ceiling surface of the second gas flow diversion member are        arranged to abut against each other.

By the arrangement of these two gas flow diversion, when the combustiongas generated in the first combustion chamber flows from the firstthrough hole into the filter chamber, the combustion gas flow isforcibly caused to flow through the holes in the circumferential surfaceof the first diversion member to the cylindrical filter. In addition,most of the gas is discharged, after filtered and cooled, through thegas discharge port, but, even if part of the gas is not dischargedthrough the gas discharge port, the gas does not ignite nor burn thesecond gas generating agent because of the flame-transferring preventionaction obtained by the filter and the suppressing action, obtained bythe second gas diversion member, on an amount of gas flowing from thesecond through hole to the second combustion chamber.

Preferably, the gas flow diversion member is provided with a flangeportion at the opening portion so that the diversion member is disposedby sandwiching the flange portion between the first partition wall orthe second partition wall and the cylindrical filter, and thereby, acombustion flow unfailingly flows through the filter and the attachmentcan be made easily.

In the gas generator for an airbag of the present invention, a capmember corresponding to a flame-transferring preventing means is furtherarranged in the second combustion chamber, and this cap member, whichcomprises a ceiling surface, a side surface having a plurality of ventholes and an opening portion provided in the opposite side of theceiling surface, covers the second through hole at the opening portionside and is fixed to the second partition wall.

The flame-transferring prevention action is further enhanced by thecombination of a gas flow diversion member and the cap member.

The gas generator for an airbag of the present invention can be appliedin a variety of well known gas generators used in automobile airbagsystems.

The gas generator for an airbag of the present invention comprises aflame-transferring preventing means, the flame-transferring preventionaction that comprises the flame blocking action, the gas temperaturelowering action and the mist reduction action obtained by theflame-transferring preventing means is exhibited, even when thecombustion gas generated in one combustion chamber flows into the othercombustion chamber, such a malfunction does not occur that the gasgenerating agent in the other combustion chamber is ignited and burnt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial cross sectional view of a gas generator for anairbag.

FIG. 2 is a partial cross sectional view of FIG. 1.

FIG. 3 is a partial cross sectional view of an embodiment of a gasgenerator for an airbag different to FIG. 1.

FIG. 4 is a partial cross sectional view of an embodiment of a gasgenerator for an airbag different to FIG. 1.

FIG. 5 is a partial cross sectional view of an embodiment of a gasgenerator for an airbag different to FIG. 1.

FIG. 6 is a partial cross sectional view of an embodiment of a gasgenerator for an airbag different to FIG. 1.

FIG. 7 is an axial cross sectional view of an embodiment of a gasgenerator for an airbag different to FIG. 1.

FIG. 8 is an axial cross sectional view of an embodiment of a gasgenerator for an airbag different to FIG. 1.

FIG. 9 is a partial enlarged view of FIG. 8.

EXPLANATION OF NUMERALS

-   -   10 Gas generator for an airbag    -   11 Cylindrical housing    -   21 First igniter    -   23 Transfer charge    -   30 First combustion chamber    -   33 First gas generating agent    -   35 First partition wall    -   36 Second partition wall    -   40 Second combustion chamber    -   41 Second igniter    -   43 Second gas generating agent    -   50 Filter chamber    -   51 Cylindrical filter    -   52 Gas discharge port    -   61 First through hole    -   62 Second through hole    -   70 First cap member    -   75 Second cap member    -   80 Gas-flow inhibiting member

EMBODIMENTS OF THE INVENTION (1) First Embodiment

With reference to FIG. 1 and FIG. 2, a gas generator for an airbagincluding a flame-transferring preventing means will be described. FIG.1 is a cross-sectional view in the axial direction of the gas generator,and FIG. 2 is a partial cross-sectional view of FIG. 1.

A first ignition means chamber 20 and a first combustion chamber 30 areaxially arranged in one end side of a cylindrical housing 11. Thecross-sectional shape in the widthwise direction of the cylindricalhousing 11 is not limited to a circular shape, but may be an ellipticalor polygonal shape.

The first ignition means chamber 20 is enclosed by a retainer 22 and thecylindrical housing 11, and accommodates a first igniter 21 therein.

The first igniter 21 is fixed by a crimped portion 12 in the end portionperipheral edge of the cylindrical housing 11 and an annular crimpedportion 13. The numeral 15 denotes an O-ring for securing themoisture-proof.

The retainer 22 is press-inserted into the cylindrical housing 11 and,although it cannot be moved towards the first igniter 21 due to theannular crimped portion 13, it is formed to be movable in the reversedirection.

A transfer charge 23 is stored in the first ignition means chamber 20(for example, a well-known transfer charge such as B/KNO₃, or a moldedarticle of gas generating composition formed into the desired shape,having a combustion temperature of 1700 to 3000° C.).

The first combustion chamber 30 is enclosed by the retainer 22, thecylindrical housing 11 and a first partition wall 35. A first gasgenerating agent 33 is stored in the first combustion chamber 30 (forexample, a molded article of gas generating composition formed into thedesired shape, having a combustion temperature of 1000 to 1700° C.). Adesired volume of the first combustion chamber 30 can be obtained byadjusting an axial position of the retainer 22.

The first ignition means chamber 20 and the first combustion chamber 30are in communication with each other through a plurality ofcommunication holes 24 provided in the retainer 22.

A second combustion chamber 40 is arranged in the other end side of thecylindrical housing 11. A second igniter 41 is accommodated in thesecond combustion chamber 40 and is fixed by a crimped portion 16 in theend portion peripheral edge of the cylindrical housing 11 and an annularcrimped portion 17. The numeral 18 denotes an O-ring for securing themoisture-proof.

A second gas generating agent 43 (for example, a molded article of gasgenerating composition formed into the desired shape, having acombustion temperature of 1000 to 1700° C.) is stored in the secondcombustion chamber 40.

A filter chamber 50 sandwiched between the first partition wall 35 and asecond partition wall 36 is provided in the central portion of thecylindrical housing 11. The first partition wall 35 and second partitionwall 36 are fixed by crimping the cylindrical housing 11 (crimpedportions 56, 58 and crimped portions 55, 57).

A cylindrical filter 51 is disposed in the filter chamber 50 in theaxial direction of the housing, and a plurality of gas discharge ports52 are provided in a wall surface of the cylindrical housing 11 facingthe cylindrical filter 51.

The cylindrical filter 51 is press-supported in the diametral directionat two positions by the annular crimped portions 55, 56, and, because oftwo annular crimped portions 55, 56, the gap is secured between theouter circumferential surface of the annular filter 51 and the innerwall surface 11 a of the cylindrical housing 11 (plurality of gasdischarge ports 52).

In order to enhance the moisture-proof in the first combustion chamber30 and the second combustion chamber 40, the plurality of gas dischargeports 52 are covered by an aluminium or stainless steel seal tape 53.

A single first through hole 61, which corresponds to an entrance to agas discharge passage extending from the first combustion chamber 30 tothe gas discharge port 52, is provided in the first partition wall 35,and

-   -   the first through hole 61 is covered by the first cap member 70        from the first combustion chamber 30 side. The first cap member        70 comprises a ceiling surface 72 and side surface 73, the        opposite side of the ceiling surface 72 includes an opening        portion, and a plurality of vent holes 71 are provided in the        side surface 73. A cross sectional shape of the first cap member        70 is not limited to a circular shape but may be an elliptical        or polygonal shape.

The first cap member 70 comprises a flange portion 74 in the openingportion peripheral edge, and the flange portion 74 and the firstpartition wall 35 are fixed together by crimping the cylindrical housing11.

A second through hole 62, which corresponds to an entrance to a gasdischarge passage extending from the second combustion chamber 40 to thegas discharge port 52, is provided in the second partition wall 36, andwhile the diameter of the second through hole 62 is set to be smallerthan the diameter of the first through hole 61, both diameters aresmaller than the inner diameter of the cylindrical filter 51.

The second through hole 62 is covered by the second cap member 75 fromthe second combustion chamber 40 side. The second cap member 75comprises a ceiling surface 77 and side surface 78, the opposite side ofthe ceiling surface 77 includes an opening portion, and a plurality ofvent holes 76 are provided in the side surface 78. The cross sectionalshape of the second cap member 75 is not limited to a circular shape butmay be an elliptical or polygonal shape. The second cap member 75comprises a flange portion 79 in the opening portion peripheral edge.

A cylindrical gas-flow inhibiting member 80 is disposed inside thesecond cap member 75, and this assembly functions as aflame-transferring preventing means.

In the cylindrical gas-flow inhibiting member 80, one end openingportion 81 faces the second through hole 62 and the other end openingportion 82 faces the ceiling surface 77 of the cap member 75, and theinhibiting member is arranged concentrically with the second cap member75. The gas-flow inhibiting member 80 comprises a flange portion 84 inthe peripheral edge of the opening portion 81.

Since the circumferential surface 83 of the cylindrical gas-flowinhibiting member 80 and the side surface 78 of the second cap member 75are directly opposite to each other, the circumferential surface 83 andvent holes 76 are also directly opposite to each other. A gap isprovided between the other end opening portion 82 and the ceilingsurface 77, and the interval of this gap is adjusted in accordance withan amount of a combustion gas generated in the second combustion chamber40.

In this embodiment, in order to adjust the combustibility of the secondgas generating agent 43 in the second combustion chamber 40 by thesecond though hole 62, the total opening area of the vent holes 76, thecross-sectional area of the circumferential surface 83 of the gas-flowinhibiting member 80 and the side surface 78 of the cap member 75 andthe cross-sectional area between the peripheral edge of the other endopening portion of the gas-flow inhibiting member 80 and the ceilingsurface 77 of the cap member 75 are all formed larger than the openingarea of the second through hole 62.

The respective flange portions 79, 84 of the second cap member 75 andthe gas-flow inhibiting member 80 abut against the second partition wall36 and are fixed together by further crimping the cylindrical housing 11(crimped portion 57).

It should be noted that, in this embodiment, a member identical to thegas-flow inhibiting member 80 can also be arranged in the first capmember 70. In this case, mainly, a mist reduction action is exhibited.

Next, with reference to FIG. 1 and FIG. 2, an operation of the gasgenerating agent 10 when assembled in an air bag system installed in anautomobile will be described. In the following, a case such that thefirst igniter 21 and the second igniter 41 are activated with a slighttime lag is described. The arrow in FIG. 2 illustrates a firstcombustion gas flow.

At the vehicle collision, the first igniter 21 is activated to igniteand burn the transfer charge 23, so that an ignition energy (a hightemperature gas or flame) is generated. This ignition energy flowsthrough the through hole 24 into the first combustion chamber 30 toignite and burn the first gas generating agent 33.

The first combustion gas generated by the combustion of the first gasgenerating agent 33 flows through the vent holes 71 into the first capmember 70, passes through the first through hole 61, and then flows intothe filter chamber 50. Thereafter, the first combustion gas is cooledand the combustion residue thereof is filtered as it passes through thecylindrical filter 51, the gas breaks the seal tape 53 and is dischargedthrough the gas discharge port 52 to inflate an airbag.

In such a discharging process of the first combustion gas, part of thefirst combustion gas sometimes flows from the filter chamber 50 into thesecond through hole 62. At this time, because of the existence of thecylindrical gas inhibiting member 80 arranged in the second cap member75, the first combustion gas does not advance directly to the vent holes76 but flows through the vent holes 76 into the second combustionchamber 40 after it strikes against the ceiling surface 77 and changesits direction.

As described above, the first combustion gas does not advance directlybut advances in a zigzag way, and therefore, the flame-preventing actionis exhibited in this process. Consequently, the second gas generatingagent 43 is never ignited and burnt by the first combustion gas flowinginto the second combustion chamber 40.

When the second igniter 41 is activated later, the second gas generatingagent 43 is ignited and burned to generate a second combustion gas. Thesecond combustion gas (which includes the first combustion gas that hasflowed into the second combustion chamber 40) flows through the ventholes 76 into the second cap member 75, passes through a zigzag passagebecause of the presence of the cylindrical gas-flow inhibiting member80, and then flows from the second through hole 62 into the filterchamber 50. At this time, the second combustion gas strikes against thesecond cap member 75 and the cylindrical gas-flow inhibiting member 80,so that mists are collected and an amount thereof is reduced.

Thereafter, the second combustion gas is cooled and the combustionresidues thereof are filtered as it passes through the cylindricalfilter 51, and it is then discharged through the gas discharge port 52to further inflate the airbag.

(2) Second Embodiment

A gas generator for an airbag including a flame-transferring preventingmeans will be described with reference to FIG. 1 and FIG. 3.

FIG. 3 is a partial cross sectional view of a gas generator of adifferent embodiment from FIG. 1. The arrow in FIG. 3 indicates a firstcombustion gas flow.

The basic structure of the gas generator of FIG. 3 is identical to thatof FIG. 2, except for a sealing tape 90 closing, from the inside, all orpart (preferably all) of the vent holes 76 in the second cap member 75.

When the first combustion gas enters the second cap member 75, its flowdirection is changed because of the existence of the cylindricalgas-flow inhibiting member 80 (in other words, a gas-flow force isweakened), and thereafter, the seal tape prevents the combustion gasfrom flowing into the second combustion chamber 40. Even if the sealtape 90 is ruptured by the first combustion gas, the first combustiongas that has flowed into the second combustion chamber 40, does notignite and burn the second gas generating agent 43 because of theflame-transferring prevention action of the second cap member 75. Theseal tape 90 is easily ruptured by the second combustion gas.

It should be noted that, in this embodiment, a member identical to thegas-flow inhibiting member 80 can also be disposed in the first capmember 70 shown in FIG. 1. In this case, mainly, the mist reductionaction is exhibited.

(3) Third Embodiment

A gas generator for an airbag including a flame-transferring preventingmeans will be described with reference to FIG. 1 and FIG. 4. FIG. 4 is apartial cross sectional view of a gas generator of a differentembodiment from FIG. 1. The arrow in FIG. 4 indicates a first combustiongas flow.

The basic structure of the gas generator of FIG. 4 is identical to thatof FIG. 2, except for a wire mesh 91 provided inside the second capmember 75.

The wire mesh 91 is a cylinder formed by laminating a plurality ofcompression-molded mesh woven filters made of, for example, a plainwoven wire mesh, an expanded metal, punched metal or metal lath wiremesh or a wire rod, and the wire mesh 91 is arranged between the sidesurface 78 of the second cap member 75 and the circumferential surface83 of the cylindrical gas-flow inhibiting member 80.

When the first combustion gas enters the second cap member 75, its flowdirection is changed because of the existence of the cylindricalgas-flow inhibiting member 80 (in other words, a gas-flow force isweakened), and thereafter, the first combustion gas flows into thesecond combustion chamber 40. In this process, the flame-transferringprevention action is exhibited since the gas passes through the wiremesh 91, and therefore, the second gas generating agent 43 is neverignited and burnt.

It should be noted that, in this embodiment, a member identical to thegas-flow inhibiting member 80 can also be arranged in the first capmember 70. In this case, mainly, the mist reduction action is exhibited.

(4) Fourth Embodiment

A gas generator for an airbag including a flame-transferring preventingmeans will be described with reference to FIG. 1 and FIG. 5. FIG. 5 is apartial cross sectional view of a gas generator of a differentembodiment from FIG. 1. The arrow in FIG. 5 indicates a first combustiongas flow.

The basic structure of the gas generator of FIG. 5 is identical to thatof FIG. 2, except for a coolant/filter 92 provided inside the second capmember 75.

The coolant/filter 92 is a cylinder formed by laminating a plurality ofcompression-molded mesh woven filters made of, for example, a plainwoven wire mesh, an expanded metal, punched metal or metal lath wiremesh or a wire rod, and the coolant/filter 92 is disposed between theceiling surface 77 of the second cap member 75 and the other end openingportion 82 of the cylindrical gas-flow inhibiting member 80.

When the first combustion gas enters the second cap member 75, the gaspasses through the coolant/filter 92 in the process in which its flowdirection is changed because of the existence of the cylindricalgas-flow inhibiting member 80, and then the first combustion gas flowsinto the second combustion chamber 40. In this process, theflame-transferring prevention action is exhibited, and therefore, thesecond gas generating agent 43 is never ignited and burnt.

The Embodiment in which the coolant/filter 92 is used is suitable whenan amount of the first combustion gas generated in the first combustionchamber 20 is particularly large (that is, when a pressure produced bythe fist combustion gas is large). It should be noted that, in thisembodiment, a member identical to the gas-flow inhibiting member 80 canalso be arranged in the first cap member 70. In this case, mainly, themist reduction action is exhibited.

(5) Fifth Embodiment

A gas generator for an airbag including a flame-transferring preventingmeans will be described with reference to FIG. 1 and FIG. 6. FIG. 6 is apartial cross sectional view of a gas generator of a differentembodiment from FIG. 1. The arrow in FIG. 6 indicates a first combustiongas flow.

The basic structure of the gas generator of FIG. 6 is identical to thatof FIG. 2, except for a covering member which is provided at the secondpartition wall inside the filter chamber 50 to prevent the firstcombustion gas flow from advancing directly to the second through hole62.

The covering member 93 comprises a disk portion 93 a and a supportportion 93 b larger than the second through hole 62, and the supportportion 93 b is press-supported between the end surface of thecylindrical filter 51 and the second partition wall 36. The disk portion93 a is held by the support portion 93 b such that a gap is obtainedbetween the portion 93 a and the second through hole 62 and that theperipheral edge portion is prevented from abutting against the innercircumferential surface of the cylindrical filter 51.

The first combustion gas, which has entered the filter chamber 50,strikes against the covering member 93, and its flow is then disturbed,so that an amount of the first combustion gas to enter the second capmember 75 is smaller than that in the first embodiment. In the same wayas the first embodiment, a flame-transferring prevention action isexhibited when the first combustion gas enters the second cap member 75.It should be noted that, in this embodiment, a member identical to thegas-flow inhibiting member 80 can also be arranged in the first capmember 70. In this case, mainly, the mist reduction action is exhibited.

(6) Sixth Embodiment

A gas generator for an airbag including a flame-transferring preventingmeans will be described with reference to FIG. 1 and FIG. 7. FIG. 7 is across sectional view of a gas generator of a different embodiment fromFIG. 1.

The basic structure of the gas generator of FIG. 7 is identical to thatof FIG. 1, except that all of the first through holes provided in thefirst partition wall portion 35 and all of the second through holesprovided in the second partition wall 36 are not directly opposite toeach other in the axial direction.

Most of the first combustion gas flow, which has flowed from the firstthrough hole 61 into the filter chamber 50, flows to the gas dischargeport 52, and even if part of the combustion gas flows toward the secondthrough hole 62, it does not advance directly from the first throughhole 61 to the second through hole 62 but flows from the second throughhole 62 into the second cap member 75 after having collided with thesecond partition wall 36 surface.

Because the flow of the first combustion gas, which has flowed into thefilter chamber 50, is disturbed as it collides with the second partitionwall 36 surface, an amount of first combustion gas entering the secondcap member 75 is smaller than that in the first embodiment. It should benoted that, in the same way as the first embodiment, aflame-transferring preventing action is exhibited when the firstcombustion gas enters the second cap member 75. In this embodiment, amember identical to the gas-flow inhibiting member 80 can also bearranged in the first cap member 70. In this case, mainly, the mistreduction action is exhibited.

(7) Seventh Embodiment

A gas generator for an airbag including a flame-transferring preventingmeans will be described with reference to FIG. 8 and FIG. 9. FIG. 8 is across sectional view of a gas generator of a different embodiment fromFIG. 1, and FIG. 9 is a partial enlarged view of FIG. 8. The basicstructure of the gas generator of FIG. 8 is identical to that of FIG. 1,so that only different part from FIG. 1 will be described.

A first gas flow diversion member 100 and second gas flow diversionmember 110 are adjacently disposed in the axial direction inside thefilter chamber 50. It is desirable that the volume ratio of the firstgas flow diversion member 100 and second gas flow diversion member 110be proportional to amounts of gases generated in the first combustionchamber 30 and the second combustion chamber 40.

The first gas flow diversion member 100 comprises a ceiling surface 101and a circumferential surface 103 having a plurality of vent holes 102,an opening portion 104 is provided in the opposite side of the ceilingsurface 101, and a flange portion 105 is provided in the opening portion104.

The circumferential surface 103 abuts against the inner circumferentialsurface of the cylindrical filter 51 and covers the first through hole61 from the opening portion 104 side, and the flange portion 105 issandwiched between the first partition wall 35 and an end surface of thecylindrical filter 51 and is fixed together with the first partitionwall 35 by the crimped portions 56, 58. The flange portion 105 may befixed to the first partition wall 35 by welding instead of crimping.

The second gas flow diversion member 110 comprises a ceiling surface 111and a circumferential surface 113 having a plurality of vent holes 112,an opening portion 114 is provided in the opposite side of the ceilingsurface 111, and a flange portion 115 is provided in the opening portion114.

The circumferential surface 113 abuts against the inner circumferentialsurface of the cylindrical filter 51 and covers the second through hole62 from the opening portion 114 side, and the flange portion 115 issandwiched between the second partition wall 36 and the end surface ofthe cylindrical filter 51 and is fixed together with the secondpartition wall 36 by crimped portions 55, 57. The flange portion 115 maybe fixed to the second partition wall 36 by welding instead of crimping.

The ceiling surface 101 of the first gas flow diversion member 100 andthe ceiling surface 111 of the second gas flow diversion member 110 abutagainst each other.

It should be noted that only one of the first gas flow diversion member100 and the second gas flow diversion member 110 may be arranged. Inaddition, the embodiments of FIG. 8 and FIG. 9 do not comprise the firstcap member 71 in FIG. 1.

The combustion gas generated in the first combustion chamber 30 flowsfrom the first through hole 61 into the first gas flow diversion member100, and because the movement thereof in the axial direction isinhibited by the first gas flow diversion member 100 and the second gasflow diversion member 110, the combustion gas flows through the ventholes 102 of the circumferential surface 103 into the cylindrical filter51. Thereafter, most of the combustion gas is discharged through the gasdischarge port 52 to inflate the airbag, but sometimes, part of thecombustion gas moves axially inside the cylindrical filter 51 and flowsthrough the vent holes 112 of the circumferential surface 113 into thesecond gas flow diversion member 110. Thereafter, passing through thesecond through hole 62 and the cap member 75, the combustion gas flowsinto the second combustion chamber 40.

The flame-preventing action by the cylindrical filter 51 is exhibited(cooling of first combustion gas and capture of mists contained in thegas) in this process, and an amount of flow into the second gas flowdiversion member 110 is suppressed by the circumferential surface 113and the vent holes 112. Furthermore, the flame-preventing action by thecap member 75 is also exhibited.

As a result, even if the combustion gas flows into the second combustionchamber 40, the second gas generating agent 43 is not ignited andburned. In addition, not only in the case such that the second igniter41 is activated later but also in the case such that only the firstigniter 21 is activated, the second gas generating agent 43 is neverignited and burned.

1. A gas generator for an airbag, comprising two combinations of anignition means and a combustion chamber including a gas generatingagent, the two ignition means capable of being activated separately fromeach other with a time lag, the gas generator having a structure suchthat part of the combustion gas possibly flows from a gas dischargepassage into the other combustion chamber in a procedure where one ofthe ignition means is activated first, the gas generating agent in oneof the combustion chambers is ignited and burnt first to generate acombustion gas and the combustion gas flows in the gas discharge passageand is discharged from a gas discharge port to inflate an air bag, atleast one flame-transferring preventing means being provided at a givenposition in the passage where the combustion gas flows from the gasdischarge passage into the other combustion chamber for obstructingdirect advance of the combustion gas flow.
 2. The gas generator for anair bag according to claim 1, wherein the flame-transferring preventingmeans comprises a combination of a cap member and a gas-flow inhibitingmember arranged in the interior of the cap member, the cap membercomprises a ceiling surface and a side surface having a plurality ofvent holes, the opposite side of the ceiling surface comprises anopening portion, and the gas-flow inhibiting member is arranged suchthat, when a combustion gas flows from the gas discharge passage andenters the cap member through the opening portion of the cap member, thedirection of the combustion gas is changed by the gas-flow inhibitingmember and then the gas flow enters, through the vent holes of the sidesurface, the other combustion chamber (second combustion chamber) inwhich combustion is started with delay.
 3. The gas generator for anairbag according to claim 1 or 2, wherein the flame-transferringpreventing means comprises a seal tape, and by the seal tape, thecombustion gas flow is prevented from entering the other combustionchamber in which combustion is started with delay.
 4. The gas generatorfor an airbag according to claim 1 or 2, wherein the flame-transferringpreventing means comprise a wire mesh or coolant/filter, the combustiongas flow flows, through the wire mesh or coolant/filter, into the othercombustion chamber in which combustion is started with delay.
 5. The gasgenerator for an airbag according to claim 1 or 2, wherein the gasdischarge passage itself has a structure for obstructing the directadvance of the combustion gas flow.
 6. The gas generator for an airbagaccording to claim 1, wherein a coolant/filter is arranged, separatelyto the flame-transferring preventing means, in the gas discharge passagethat leads to the gas discharge port, and when part of the combustiongas flows into the other combustion chamber, the combustion gas alwayspasses through the coolant/filter to enter the other combustion chamberbecause of the action of the flame-transferring means for obstructing adirect advance of the combustion gas flow.
 7. A gas generator for anairbag, comprising a first ignition means and a first combustion chamberaccommodating a first gas generating agent in one end side of acylindrical housing, and a second ignition means and a second combustionchamber accommodating a second gas generating agent in the other endside of a cylindrical housing, a first partition wall having a firstthrough hole and a second partition wall having a second through holedefining a separated space between the first combustion chamber and thesecond combustion chamber, a space formed between the first partitionwall and the second partition wall including a filter chamber providedwith a cylindrical filter, the cylindrical housing having a gasdischarge port provided in the surface directly facing the cylindricalfilter, a cap member being provided as a flame-transferring preventingmeans in the second combustion chamber, the cap member having a ceilingsurface and a side surface having a plurality of vent holes, providedwith an opening portion in the opposite side of the ceiling surface, thecap member covering the second through hole from the opening portionside, being fixed onto the second partition wall.
 8. The gas generatorfor an airbag according to claim 7, wherein the flame-transferringpreventing means comprises a combination of a cap member and acylindrical gas-flow inhibiting member arranged in the interior of thecap member, a cylindrical gas-flow inhibiting member is concentricallyprovided inside the cap member to have one end opening portion facingthe second through hole and the other end opening portion facing theceiling surface of the cap member, and when the combustion gas flowsthrough the second through hole into the cap member, the directionthereof is changed by the gas-flow inhibiting member, and then the gasflow enters the second combustion chamber through the vent holes in theside surface.
 9. The gas generator for an airbag according to claim 7 or8, wherein the flame-transferring preventing means comprises a sealtape, and the vent holes of the cap member are closed by the seal tape.10. The gas generator for an airbag according to claim 7 or 8, whereinthe flame-transferring preventing means comprises a wire mesh arrangedbetween the side surface of the cap member and the side surface of thegas-flow inhibiting member, the combustion gas is caused to flow intothe other combustion chamber in which the initiation of combustion isdelayed after passing through the above wire mesh.
 11. The gas generatorfor an airbag according to claim 7 or 8, wherein the flame-transferringpreventing means comprises a coolant/filter disposed between the ceilingsurface of the cap member and the other end opening portion of thegas-flow inhibiting member, the combustion gas is caused to flow throughthe coolant/filter into the other combustion chamber in which theinitiation of combustion is delayed.
 12. The gas generator for an airbagaccording to claim 7 or 8, wherein a covering member, which prevent thedirect advancement of the combustion gas flow to the second throughhole, is provided on the second partition wall surface inside the filterchamber.
 13. The gas generator for an airbag according to claim 7 or 8,wherein no part of the first through hole directly faces any part of thesecond through hole in the axial direction.
 14. A gas generator for anairbag, comprising a first ignition means and a first combustion chamberaccommodating a first gas generating agent in one end side of acylindrical housing, and a second ignition means and a second combustionchamber accommodating a second gas generating agent in the other endside of a cylindrical housing, a first partition wall having a firstthrough hole and a second partition wall having a second through holedefining a separated space between the first combustion chamber and thesecond combustion chamber, a space formed between the first partitionwall and the second partition wall including a filter chamber providedwith a cylindrical filter, the cylindrical housing having a gasdischarge port provided in the surface directly facing the cylindricalfilter, wherein at least one gas flow diversion members being disposedin the filter chamber to forcibly make the combustion gas flow enter thecylindrical filter when the combustion gas generated in the firstcombustion chamber flows into the filter chamber from the first throughhole.
 15. The gas generator for an airbag according to claim 14, whereinthe gas flow diversion member comprises a ceiling surface and acircumferential surface having a plurality of vent holes, and an openingportion is provided in the opposite side of the ceiling surface, asingle gas flow diversion member is arranged such that a gapcorresponding to a passage for gas flow is secured between the secondthrough hole and ceiling surface, the circumferential surface abutsagainst the inner circumferential surface of the cylindrical filter andthe diversion member covers the first through hole at the openingportion side and is fixed to the first partition wall.
 16. The gasgenerator for an airbag according to claim 14, wherein two gas flowdiversion members is provided, among these, a first gas flow diversionmember, which comprises a ceiling surface, a circumferential surfacehaving a plurality of vent holes and a opening portion provided in theopposite side of the ceiling portion, is arranged such that thecircumferential surface abuts against the inner circumferential surfaceof the cylindrical filter and the diversion member covers the firstthrough hole at the opening portion side and is fixed to the firstpartition wall, a second gas flow diversion member, which comprises aceiling surface, a circumferential surface having a plurality of ventholes and a opening portion provided in the opposite side of the ceilingportion, is arranged such that the circumferential surface abuts againstthe inner circumferential surface of the cylindrical filter and thediversion member covers the second through hole at the opening portionside and is fixed to the second partition wall, and the ceiling surfaceof the first gas flow diversion member and the ceiling surface of thesecond gas flow diversion member are arranged to abut against eachother.
 17. The gas generator for an airbag according to claim 14 or 15,wherein a cap member corresponding to a flame-transferring preventingmeans is further arranged in the second combustion chamber, and this capmember, which comprises a ceiling surface, a side surface having aplurality of vent holes and an opening portion provided in the oppositeside of the ceiling surface, covers the second through hole at theopening portion side and is fixed to the second partition wall.